Method for producing castings in a permanent mold

ABSTRACT

Hollow castings are produced in a permanent mold having a hollow refractory core disposed in the interior of the mold. The core has a number of small sprues through which the casting cavity of the mold is filled, and excess metal is retained within the core to feed shrinkage within the interior of the casting. After the surface of the casting has chilled, the mold is separated from the casting to prevent binding, but the core is retained therein until the casting has completely solidified. The core and solidified metal therein are then removed.

United States Patent Richard C. Costello West Chicago;

Albert J. Jean, Forest Park; William J. Kucera, Elmhurat, all of 111.

Inventors Appl. No. 860.294

Filed Sept. 23, 1969 Patented Dec. 14,1971

Assignee Amsted Industries incorporated Chicago, Ill.

METHOD FOR PRODUCING CASTINGS IN A PERMANENT MOLD 2 Claims, 3 DrawingFigs.

US. Cl 164/113, 164/1 3| Int. Cl B22d 15/00 Field of Search 164/61, 70,

[ 56] References Cited UNITED STATES PATENTS 971,045 9/1910 Kerr et a1164/163 X 1,172,363 2/1916 Jones 164/363 2,326,758 8/1943 Chaplin249/142 X 3,081,488 3/1963 Casavina .L 18/45 R X Primary ExaminerJ.Spencer Overholser Assistant Examiner-John S. Brown Attorneys-Walter L.Schlegel, Jr. and Russell W. Pyle ABSTRACT: Hollow castings are producedin a permanent mold having a hollow refractory core disposed in theinterior of the mold. The core has a number of small sprues throughwhich the casting cavity of the mold is filled, and excess metal isretained within the core to feed shrinkage within the interior of thecasting. After the surface of the casting has chilled, the mold isseparated from the casting to prevent binding, but the core is retainedtherein until the casting has completely solidified. The core andsolidified metal therein are then removed.

Patented Dec. 14, 1971 2 Sheets-Sheet 2 METHOD FOR PRODUCING CASTINGS INA PERMANENT MOLD This invention relates to a method and apparatus forproducing hollow castings and more particularly to a permanent moldhaving a separate refractory core and a method for its use.

The use of permanent and semiperrnanent molds is an expediency wellknown to those skilled in the art of foundry practices. Permanent molds,made up from a plurality of mating parts composed of rigid chillmaterials, such as graphite, cast iron, steel, or water cooled copper,have been used to produce cast structures of various simple shapes. Dueto the rigidity of the mold structure, however, the casting of complexshapes has not been feasible because of possible binding up of moldparts and because the unyielding nature of the mold, which maycontribute to faults, hot tears and other defects in the casting.

Accordingly, an object of the present invention is the provision ofmeans for producing complex castings in a permanent mold, especiallywhere the casting is to be formed with a hollow central area.

Other objects will become apparent from the following description andappended claims, taken in connection with the accompanying drawingswherein:

FIG. I is a vertical sectional view of a metal casting system thatincorporates features of the presently described invention;

FIG. 2 is a vertical sectional view of the mold and core assembly of thepresent invention; and

FIG. 3 is a fragmentary plan view of the structure shown in FIG. 2.

Referring in greater detail to FIG. I, the assembly shown comprises amold, generally indicated at 10, which is filled with molten metal fromthe bottom thereof by means of a pressure casting apparatus. Suchapparatus comprises a refractory lined ladle 12 containing molten metalI3 disposed in a pressure tank or pit 14, with a cover I6 releasablysealed on said pit by means of clamps 18. A refractory pouring tube iscentrally disposed within the ladle I2 and extends upward through anopening 17 in the cover where said tube terminates in a tapered annularhead 22 supported upon said cover. A source of controlled pressurizedpneumatic fluid (not shown) is connected to a line 24 leading into thepressure tank 14, such that the molten metal 113 in the ladle 12 may bepressurized and forced upward into the casting cavity 26 of the moldIll.

The mold 110, as best shown in FIGS. 1-3, comprises a pair of matingcheek sections 28 and 30, enclosed at the top and bottom thereof byrespective cope and drag plates 32 and 3A to define the casting cavity26. The cope and drag plates may be formed from two mating pieces, tofacilitate disassembly, as will be hereinafter described. The mold partsare preferably composed of graphite, but other chill materials orcombinations thereof may be employed, such as cast iron, steel orwatercooled copper. The casting cavity 26 may be formed in any desiredconfiguration to impart shape to the cast article; the configurationshown in the present instance is that for producing a track roller fortrack-laying vehicles, said roller having a cylindrical openingtherethrough for eventual mounting on an axle or shaft.

An outer steel jacket 36 (FIG. 2) is provided around the cheek sections,and the respective cope and drag plates 32 and 34 are secured in steelflanged retainers 38 and 40, respectively. As shown in FIGS. I or 2, thedrag retainer 40 has an opening 42 therethrough lined with a refractoryannulus 44, the lower flat surface d6 of said retainer being slidablysupported upon the upper flat surface 48 of a base 50 having a similaropening 52 and refractory liner 54, said base being adapted to fit overand rest on the tapered annular head 22 of the pouring tube 20. Whenassembled, as seen in FIG. I, the bore of the pouring tube is incommunicative alignment with the opening 52 in the base and the opening42 in the drag retainer 40. A hydraulic cylinder 56 (FIG. I) isconnected between an independent support 56 and the drag retainer 40,which allows said retainer to be moved horizontally on the base fill toseal off and retain molten metal in the mold after the filling thereof.The cope plate 32 includes a plurality of openings 60 (FIGS. 2 and 3)each containing a graphite vent plug 62 having a plurality of smallpassages therethrough, which allows the escape of hot gasses from themold during the filling operation but chills and prevents leakage ofmolten metal after filling of the mold. Corresponding openings 64 areprovided in the cope retainer 33.

FIG. 2 shows an alternative arrangement for sealing off flow of moltenmetal from the mold, wherein a slide cutoff 66 having an opening 63 ispositioned between the drag plate 34 and drag retainer 4H1) and may bemoved horizontally to a closed position.

Means are provided in the interior of the mold cavity to allow fillingof the cavity and feeding of metal to the casting during solidification.For this purpose, as best shown in FIGS. 2 and 3, aligned circularopenings are provided in the drag plate 34, the cope plate 32, and thecope retainer 38 at 70, 72 and 76, respectively. A refractory tube 76 isdisposed in openings 70, 72 and 76 throughout the full height of thecasting cavity 26 and extends upward beyond the top of the cope retainer38. The tube is preferably composed of a refractory sand bonded with anorganic binder, which allows loss of rigidity during solid statecontraction of the casting. Circumferentially spaced vertical ventpassages 73 (FIGS. 2 and 3), communicating with the atmosphere at 79,are provided in the tube 76 to allow egress of gas evolved :in thedecomposition of the organic binder.

A plurality of sprues or openings generally indicated at 80, in the sideof the tube 76 provide communication between the bore 82 of the tube andthe casting cavity 26. Preferably, such openings are tapered from thebore 32 of the tube 76 to the casting cavity 26. As shown in FIG. 2,such openings may comprise an opening from the bore of the tubecommunicating with a relatively small coaxial opening from the outersurface of the tube. The number and spacing of the openings 80 are suchthat the casting cavity may be filled without undue turbulence and thatshrinkage of the casting may be adequately fed.

In operation, molten metal is introduced into the cavity 26 through thesprues 80 of the tube 76 until the cavity is completely filled and thetube is filled to a level above the cope surface, thereby furnishingfeed metal for the casting. Pouring is then terminated by activating thehydraulic cylinder 36 and sliding the mold over on the base, as shown inFIG. 1, or by moving the slide cutoff 66 illustrated in FIG. 2 to aclosed position.

After the outer surface of the casting has chilled, the mold parts areseparated from the casting and removed, while the refractory tube 76 isretained. The metal in the tube 76 remains molten because of thesurrounding envelope of molten steel in the casting, which allows aferrostatic head to be maintained to feed the casting through. thesprues 80. It may thus be seen that the sprues 80 are preferably locatedat or near the last portion of the casting to solidify.

It will also be understood that the mold Ill) may also be filled fromthe top by any suitable means, such as a bottom pour ladle. For thispurpose, a steel plug is placed in the opening 42 of the drag retainerll), and molten metal is introduced at the open top of the tube 76.

After the casting has completely solidified, the remaining metal in thecore is attached to the casting only in the area of the sprues 30, andthe core may be removed with a hydraulic punch on a press, therebyresulting in a. casting with a hollow core.

Having thus described the invention, what is claimed is:

I. In a method for producing ferrous castings in a rigid chill moldhaving a casting cavity, the steps of introducing molten metal into saidcasting cavity through a hollow refractory core disposed in said cavityand having restricted sprues therein communicating with said castingcavity, filling said casting metal into said casting cavity through aplurality of restricted passages in an insulated core disposed withinsaid casting cavity, filling said core and the entire casting cavitythrough said restricted passages, allowing said casting to solidifyagainst the chilled surfaces of said mold away from said core whilemaintaining the metal in said core in molten state, separating andremoving the mold from said casting, and feeding the shrinkage of thesolidifying casting through said restricted passages from said core.

t I I! i i

1. In a method for producing ferrous castings in a rigid chill moldhaving a casting cavity, the steps of introducing molten metal into saidcasting cavity through a hollow refractory core disposed in said cavityand having restricted sprues therein communicating with said castingcavity, filling said casting cavity through said sprues, establishing aferrostatic head of molten metal in said core above said casting cavityto feed shrinkage in said casting through said sprues duringsolidification, separating and removing the mold from said casting whenthe outer surface thereof is chilled and the interior thereof is atleast partially molten, allowing said casting to solidify, and removingsaid core and any metal solidified therein from said casting.
 2. In amethod for producing ferrous castings in a rigid chill mold having acasting cavity, the steps of introducing molten metal into said castingcavity through a plurality of restricted passages in an insulated coredisposed within said casting cavity, filling said core and the entirecasting cavity through said restricted passages, allowing said castingto solidify against the chilled surfaces of said mold away from saidcore while maintaining the metal in said core in molten state,separating and removing the mold from said casting, and feeding theshrinkage of the solidifying casting through said restricted passagesfrom said core.